Liquid treating process and apparatus



June 17, 1941. w, GREEN 2,245,583

LIQUID TREATING PROCESS AND APPARATUS Filed June 2, 1938 IN VENTOR.

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Patented June 1 7, 1941 LIQUID TREATING PROCESS AND APPARATUS WalterGreen, Chicago, 111., assignorjto International Filter (30., Chicago;111., a corporation of Delaware Application June 2, 1938, Serial No.211,362

g 11 Claims; (01. 210-16) This invention relates to a method and apparatus for removal of substances from liquids in solid form, the processhaving principal applications in the softening, clarification andstabilization of water. The process involves the continuous formation,conditioning and removal of precipitates by establishing in a body ofthe liquid to be treated a mixing and reaction zone and a, clarificationzone and providing an improved type of circulation pattern whichincludes the re-use of solids separated from previously treated liquids.

A principal object of the invention is the treatment of water containinghardness-imparting substances such as calcium and magnesium by-effecting a reaction for the formation of solids in the presence ofpreviously separated solids which are maintained in a state ofsuspension and substantially unitary rotation and passing water from themixing and reaction zone uniformly upwardly through vertical baflieswhich prevent the rotation of the reaction zone from extendingtherebetween.

Another object of the invention is the softening of water in a verticaltank in which there is provided in the bottom portion of the tank ameans for maintaining a suspension comprised of water undergoingtreatment and suspended solids sepa-' rated from previously treatedwater and in the upper portion of the tank there are provided uprightbaflies to form relatively quiescent separation or clarification zones.

A still further object of this invention is the provision of a watersoftening process in which there is established and maintained in thelower portion of a tank a body of water containing crystalline particles'of hardnes's imparting constituents separated from previously treated"water, the softening reaction being effected in the pres-' ence ofthese previously precipitated solids while; the body of water ismaintained in a state of unitar'y rotation, the water beingdisplacedupwardly from the zone of rotation at a substantially even rate of flowinto zones of relative 'quie'sence'.

A further and special object of'the invention is to provide specialmeans for reducing the solids content of water containing a'suspensionof precipitated solids, there being involved an auxiliary chamberproviding a'space open to the slurry'and of such quiescence'a s topermit settling of solids into the space to provide a concentrationthereof.-

These and further objects will be understood upon a consideration'of thefollowing description of a preferred embodiment of the invention and byreference to the accompanying drawing, in which Fig. 1 is a'verticalsection of apparatus constructed in accordance with the invention; andFig 2 is a top view, partly in section, of the embodiment shown in Fig.l.

Heretofore it has been suggested to soften and clarify water byproducing the softening reaction in part at least in a body of water towhich is imparted rotary motion, the treated water being displacedupwardly into an expanding separation zone for clarification purposes.This general type of softening process is described in my prior patent,No. 1,702,257, issued February '19, 1929, and again in Spaulding PatentNo. 2,021,672, issued November 19, 1935. The process as practicedheretofore has certain objections which are eliminated in accordancewith the present invention.

In the apparatus shown in the drawing there is provided a treating tank40 which may be of cylindrical construction. There is provided a ver-vtical shaft ll mounted centrally of the tank I'll, the shaft havingagitator blades Ilextending horizontally adjacent the lower portion ofthe tank. Supporting' wires or rods I3 maybe used stream of slurrycirculated through the sleeve 16 to be mixed with the raw water.

to assist in holding up the agitator blades l2.

Raw water to be treated is introduced into the tank adjacent the bottomthereof through line H. The raw water inlet line is .provided with adischarge section l5 which is turned along the side of thetank in thedirection of rotation of the paddle l2. Surrounding the dischargesection ,of the raw water inlet line is: an open-ended casing l6 whichis spaced from the discharge section so that slurry in the bottom of thetank can, pass through the open end of the casing and be mixed with rawwater entering the tank. The provision of a casing in this manneraccentuates the jet like effect of the discharge of raw water into thetank-and causes a definite admixture of the raw water with slurrypreviously formed in the tank.

In Fig. 2 there will be seen a stream projecting impeller H which :isoperative to increase the p A chemical feed line is shown at I8, thisline discharging in front of the. impeller 11 so that thechemicals areprojected through the sleeve i6 and mixed with circulated slurrybeforecontact 'of the slurry with the' raw water.

- tend a series of radial ballles 20 which are posi-' The tank also isprovided with a central sleeve [9, surrounding the shaft II andterminating somewhat above the bottom or the tank. Be-

tween the sleeve l9 and the wall of the tank extioned vertically in thetank and extend down- -wardly therein to a plane spaced substantiallyabove the bottom of the tank, as shown inF g.

Above the baffles 20 there is an annular weir 2i attached to andextending around the inner side or the tank and providing an overflowoutlet for water rising in the tank. An outlet line 22 communicates withthe tank adjacent weir 2| and provides a discharge line for water fromthe tank Inthe lower part of the tank there is provided an upstandingangularly disposed partition member 23. Adjacent the bottom of thepartition there is positioned a draw-oil line 24 through which liquidbetween the partition 22 and the walls of the tank can be withdrawn,

There also is provided a main blow-oi! line 25 communicating with thebottom of the tank. This line may be used to withdraw slurry from thetank or to discharge the contents of the tank as desired.

Surrounding the shaft cylinder I9 is an opentopped funnel member 26 oftruncated conical shape, the base of the cone being positioned againstand supported by the cylinder l9. The baflles preferably are providedwith triangular cut-out portions which fit around the funnel 28 andprovide in the funnel a continuous communication between the pluralityof sections formed by the baflles. In the lower portion of the conicalmember 26 is provided an opening to which is fitted a downwardlyextending conduit 22, leading to the compartment between the partition23 and the tank wall.

The funnel member 26 also has another conduit, indicated at 21, whichleads from the lower portion of the tunnel to the casing It at a pointback of the impeller H. The action of the im-' peller and the dischargeof raw water through line l draws liquid from the funnel member 26 1through the line 21 and so delivers an additional supply of solids tothe incoming water.

In the operation or the process water to be softened is flowed into thetank through the line It and chemicals such as lime and soda areintroduced through the chemical line ll. The hardness-impartingconstituents of the raw water are changed to calcium carbonate andmagnesium hydroxide, which under the conditions of the processprecipitate out into crystalline particles. The shaft II is set inrotation and agitators I2 create in the lower portion of the .tank belowthe bailies 20 a general rotary movement of the water, together withlocal mix- 'ing eddies. This rotary motion is augmented by the jet-likeeilfect oi the discharge through section l5. As the water rises in thetank it reaches the level of the lower portion of balls 2. and continuesto rise upwardly between the batfles. The bailles prevent the rotarymovement which is maintained in the bottom of the tank from extendingabove'their lower portion and thereby establish a zone of relativequiescence in the upper portion of the tank through which the treatedwater must pass in reaching the overflow 2!. In this zone of quiescencethe water has anopportunity to separate from the crystalline particlesand to rise to the top of the tank. Separation of the water from theparticles results in a concentration or the particles in the tank tobuild up a relatively thick slurry of suspended crystalline particles.The solids content of the slurry will usualy be of the order of 2 to 3per cent, but it likewise may be considerably more than this figure orless, depending upon such iactors as the type of water being treated. In

mally fill the lower part 01' the tank up to or a little above the topedge of tunnel 26.

As the solids concentration in the bottom of the tank builds up there isan increasing amount of solids mixed with the raw water and reactantduring the softening reaction. Previously treated water carryingsuspended particles passes through the casing i6 and is admixed with theraw water and chemicals and further admixture takes place in therotating slurry. It is preierred that the chemicals be mixed with theslurry before the slurry contacts the raw water.

The softening reaction then occurs in the presence oi a relatively largequantity of previously precipitated solids of like nature to those to beiormed. The unitary or general state of rotation in the bottom of thetank presents constantly changing portions of the slurry to the rawwater and maintains particles in a general state of suspension. Byefiecting the softening reaction in the presence of e previouslyprecipitated particles, there is obtained a rapid separation in solidform of the calcium carbonate and magnesium hydroxide. also, there iseffected a building up or the crystalline particles into clusters oisubstantial size which are more readily separated from the water thancrystalline particles of the type normally formed upon addition ofreagents to the water to be softened. The slurry containing thesecrystalline clusters expands upwardly in the tank by the displacementoccasioned by raw water entering the tank through line It, and as themixture passes upwardly into and through the relatively quiescent zonesprovided by bames 2|! there occurs a separation or clear water sincethere is no longer sumcient agitation to maintain the solids in theslurry mixture in suspension. settle back out or the quiescent tatlngmixture below.

There also is shown in the drawing a particularly eiiective means forreturn or recirculation of the crystalline particles to themixing andreaction zone in the bottom oi the tank or discharge to waste. When thetop level of the slurry rises above member 26 the particles pass intothe space above this funnel member and settle down into it, therebyeffecting a concentration of the solids in the lower portion of thetunnel 26. .As the solids concentrate in the funnel 26' the specificravity of the slurry in which they are suspended increases and thereresults a flow downwardly Some solids may zone into the rothrough theline 21, thereby providing a return trator 2! to the reaction zone theremay be prooperationthis thick supension or slurry will nor- 7 vided aconduit 22 leading from the iunnelmember 22 to the space behind thepartition 23. From this space the particles separated by the funnelmember 2 may be discharged to waste. The line 28 need not necessarilydischarge into the separation space provided by the partition 23, butmay Pass directly through the wall of the tank and to waste.

The concentrator 2 acts substantially the same regardless of whether thesolids are discharged through line 21 back to the casing I 6 in thereaction zone or through line 28 to waste, and may be utilized todetermine the upper level of slurry in the tank. The concentration ofslurry effected when the discharge from funnel 26 is to waste results ina saving in the amount of treated water passing to waste.

Where the return 01 solids from the funnel 26 the top edge of the funneltank Ill may be extended to form storage space.

is to casing 6 there is a concentration of solids in the reaction zone.During the first part of the process and until the concentration ofvsolids in the reaction zone has reached the desired point it ispreferred that all of the solids be returned to the reaction zone. Theincreased specific gravity of the mixture of liquid and solids in thefunnel 26 tends to cause a flow through line 21, and this flow augmentedby the action of impeller l1 and the jet efiect of the discharge of rawwater through the section IS.

The solids content of the slurry in the bottom of the, tank is greatlymore than could be obtained by the treatment of a like quantity of waterwithout concentration of the solids retained from previously treatedwater, so that a balance between the solids being formed, by thetreatment of raw water and solids removed from the tank may be eiiectedby withdrawal of a relatively small volume of the slurry in the bottomof the tank as compared with the amount of raw water being treated. Thepartition member 23 and outlet line. 24 can be used to effect a furtherconcentration of the. solids and a reduction in the amount of waternecessarily blown oil to waste to remove solids from the reaction zone.The concentration chamber provided by partition 23 hasan action somewhatsimilar to the action of cone 26, in that suspended particles in theslurry tend to settle into the space behind partition 23 where theagitating effect-of the paddles l2 does not extend. Thus, there iseffected a concentration of the solids in the lower portion of thechamber provided between the wall of the tank in themember 23 and thisconcentrated slurry may be drawn off through line 24. Partition 23 andfunnel member 26 may be made adjustable in their position to change thelevel of withdrawal of solids from the tank. The funnel member 26 has askimming action which may be used to fix the upper level of the slurryin the tank.

The general pattern of circulation of liquid in the tank includes themaintenance of a general state of rotation in the reaction zone in whichthe agitators l2 and the jet effect of the water combine to maintain theparticles of the slurry in suspension and to return changing portions ofthe slurry to the casing l-6 to be mixed with the raw water entering theprocess, water undergoing treatment being mixed and distributedthroughout the volume of the rotating slurry, and displaced therefrom asabove referred to. There is effected a general building up of particlesize and when the desired solids concentration of the water has beenreached the slurry withdrawal may be adjusted to maintain a balance.Following the general rotary motion in the bottom of the tank thedisplacement is upwardly into and through the zone of relativequiescence in which the water separates from the crystalline particles,the upflow being at substantially the same velocity throughout the tank.It is not necessary to employa separate upwardly extending separationzone of the type disclosed in my prior patent and in Spaulding PatentNo. 2,021,672. The whole area of the tank may be used for separation oftreated. water, resulting in increased capacity and saving in space.There also is obtained a more uniform and definite slurry than with myprevious patent referred to and this slurry may be more concentrated andof greater volume so that there is better contact of the water undemoinstreatment with particles and' correspondingly more rapid and betterresults. Obviously the for treated water, as in my previous patent. The

crystalline solids from the liquid may be returned directly to thereaction zone to some extent by settling out of the space between thebattles. but the return preferably is. through the funnel 26. Line 2]creates a re'turn of particles and in some cases liquid by reason of theincrease in specific gravity of the liquid in the funnel due to theconcentration of solids.- This line may have a branch, not shown,extending into the mixing and reaction .zone for direct return of solidsthereto. Line 21 provides a positive return of liquid and solids fromthe funnel 26 which does not depend upon the increase in concentrationof solids to effect the return. The impeller l1 and the jet effect ofthe raw water discharge are sumcient to pull water downwardly throughthe line 21, thereby effecting a returnof liquid=contain-' ing suspendedsolids from the zone of separation to the zone of reaction. I

It is possible to vary the'process" and appa-i ratusconsiderably fromthespecific embodiments disclosed herein for purposes of illustration andexplanation andsuchrchanges are intended included in the appendedclaims.

. I claim:

tube

1. Apparatus" of the typedescribed, comprising a substantiallycylindrical tank, an agitator in the bottomof the tank, an open-endedcasing in the lower portion-of said tank,-means for introducingliquid-to betreated in. said casing, means for introducing a reactant insaid casing, and baflle means positioned in said tank above saidagitator.

2. Apparatus of the type described, comprising a treating tank, anagitator in the lower portion of said tank, baflie members positionedabove said agitator, a solids separator positioned adjacent with liquidfrom said inlet, means for producing a current of liquid from the bottomof said tank through said casing and for producing a rota y action ofthe liquid inthe lower portion of the tank, baflie means spaced upwardlyfrom the bottom of the tank to provide a mixing and reaction zonetherebelow, a solids separator adjacent said baflies, and a solidsconcentrator below said battles.

1. Apparatus of the type described combining a substantially flatbottomed treating tank, said tank having means for delivering water tobe treated and a treating reagent into the lower portion thereof andtreated water discharge means adjacent the top thereof, agitator meansfor producing a rotary motion of liquid in the lower portion of saidtank and over substantially the whole bottom thereof, means comprisingbaflie chargingwater to be treated and for delivering treatment reagentinto a lower portion of said tank and means for discharging treatedwater from the upper portion of said tank, baflle means within said tankand serving todivide same into a lower agitating space and an upperquiescent space, agitator means in said agitator space, said bafflemeans being of form to permit free upward flow from said agitating spaceover substantially the whole area thereof and to cause substantiallyuniform rise of water over each cross-sectional area of the tank fromadjacent said agitating space to adjacent the level of said treatedliquid discharge, a solids separator having an inlet above the loweredge of said baflle means and a discharge to waste from said separator.

6. The apparatus of claim 5 comprising a second solids separator, theinlet of said second separator being at a lower level than that of thefirst referred to separator.

7. The apparatus of claim 5, comprising a second solids separator, theinlet of said second separator being of a lower level than that of thefirst mentioned separator, a conduit leading from the first mentionedsolids separator to the second mentioned, solids separator, and anadditional conduit leading from the first mentioned solids separator toadjacent the means for discharging water to be treated into said tank.

8. The apparatus of claim 2 comprising in adconduit from said solidssecond such separator, said second separator be- Y dition to the solidsseparator named therein, a separator to adJacent the inlet means.

9. The apparatus of claim 2 comprising in addition to the solidsseparator named therein a ing positioned to receive solids from anotherlevel in the tank.

10. The process of treating water that includes separation of the waterand solid particles which comprises the steps of establishing avertically rising, generally cylindrical column of water undergoingtreatment, delivering water to be treated into the lower portion of saidcolumn, accumulating in the lower portion of said column solids frompreviously treated water to form a slurry, agitating the slurry tomaintain in suspension" substantially all solids in the lower portion ofsaid column, stilling the slurry. above the zone of agitation to createa condition of relative quiescence, withdrawing solids to waste from theregion of relative quiescence, and withdrawing treated water from abovethe level of solids withdrawal.

11. The process of claim 10 comprising the step of additionallywithdrawing solids to waste from a level below the region of relativequiescence.

WALTER H. GREEN.

